Method of lubricating bearing surfaces



Fatenteoi @ec. 7, m3?

Mansion on r GAG IBE i i ACES William tney Weinrloh, Pittsburgh, has assignor to .Guli rob and lllevelopment Company, Pittsburgh, Pa, a corporation of Delaware No Drawing. Original application ilovember 12,

1935, Serial No. 49,442. Divided and this al Dlication November 18, 1936, Serial No. 111,558

iclaime.

This invention relates to methods of lubricating bearing surfaces; and it comprises a method of lubricating bearing surfaces by means of a lubricating oil of the petroleum type containin a minor amount, usually less than one per cent.

of tributyl phosphite serving to prevent decompo;

sition or the oil in storage and in use; as more fully hereinafter set forth and as claimed.

This application is a divisionbf my copending application serial No. 49,442, filed November 12,

In use and in storage all petroleum lubricating oils tend toward deterioration with various chemical'and physical changes; formation of acids, increase in carbon residue and increase in viscosity. At high temperatures these changes are more rapid and far going. lflnd that metals, in general, accelerate the deterioration of petroleum lubricating oils and that converselyyas ,the

'oils deteriorate they attack metal surfaces and noting the results. While-tributyl phosphite is.

exceptionally suitable, other esters of aliphatic alcohols are also good addition agents.

l have found that a lubricating oil containing tributyl phosphite is stabilized efiectively in storage and in use irrespective of the previous conditions in refining and of the presence or its absence of metals. Since high refining is desirable for other reasons, I regard my invention as most advantageous with the highly refined oils.

Trlbutylphosphite is a liquid, suficiently soluble in oil for my purposes, and its addition to lubricating oil is a simplemixing operation. Usually one per cent by volume or less of tributyl phosphite added to lubricating oil achieves my purpose. Good grades of Pennsylvania and Mid- Continent lubricating oils reflnedby sulfuric acid, by solvent extraction, or by aluminum chloride, with anaddition of one per cent or less by volume of tributyl phosphite give a lubricating composition not rapidly developing acidity, not corroding bearings and not developing undue viscosity when used in automotive bearings. Desirable characteristics gained-by refining to a high de gree of paraihnicity are not impaired.

Lubricating oils containing tributyl phosphite as a stabilizing agent evince great permanence both under conditions of use and when subjected to accelerated laboratory tests. One .accelerated laboratory test was made on a Pennsylvania type lubricating oil containing ml per cent by volume of tributyl phosphite.

and had the following characteristlcs'r 3112" This particular oil had been refined by the aluminum chlorideprocessj Gravity "A. P I. e Viscosity in seconds by. the saybolt' -Unif 'f versal viscometerat '100 371.0 8. U. V. at 210 F. 56.8 Viscosity index (as determined by Dean.

and Davis Chem. SzMet. 36, 618 (1929) 100.0' Carbon residue 0.06 Neutralization No. (mgm. KOH required to neutralize 1 gm. sample) 0.1

For comparative purposes this oil was treated with and without the addition of the 'tributyl phosphite. Calling the untreated oil A and the treated oil 3", in one test 10 cc. samples each of A and K were placed in 15 cc. glass tubes open at the top. The tubes were then suspended in an oil bath in suchla er as to bring the surface of the bath near the top of each tube. The bath was intained thermostatically at a temperature of 350 F. Thesamples were given time to reach the bath temperature, after which oxygen was bubbled through each sample at a controlled rate of 470 cc. per hour by means of glass capillaries projecting downwardly to a point near the bottom of the sample tube. In each instance a 5 gram strip of cadmium-silver "alloy was suspended in the sample by means of a fine copper wire.

The testing conditions were maintained for 20 hours after which the sample tubes were removed irom the bath, allowed to cool and each sample tested b identical standard methods with the following re ults:

The presence of the cadmium-silver alloy accelerated the deterioration of the oil "A" to such an extent that the viscosity became too high to measure. On the other hand, the composition X containing only 0.1 per cent of tributyl phosphite [increased (filly slightly in viscosity when subjected to the same conditions.

An increase in the neutralization number may be taken as an index of the formation of acid, and the loss in weight of the-metal strip as an index of corrosion. With this in view, the results of the tests show that the addition of tributyl phosphite greatly improved the lubricating oil as regards stability.

While I have spoken more particularly of' cadmium-silver alloys in bearing metals, 'in-' hibition of corrosion is also evidenced as regards other sensitive metal alloys used in bearings; cadmium-nickel, copper-lead, etc. My inhibition agent is also useful in alloys used with more common and less sensitive bearing metals such as steel, brass, babbitt, etc;

For the present purposes a lubricating oil may be taken to be one having a viscosity greater than 35 seconds S. U. V. at 100 F. and while I contemplate mainly stabilization of oils to be used as lubricants, stabilization is also useful when they are used for other purposes, as in trans- I formers, and as quenching oils used after heat treatments as in cooling optical glass. Quenching oils are subjected to, temperature extremes under conditions even more favorable to oxidation than those occurring in lubrication.

What I 'claim is:--'

1. A method of lubricating bearing suriacesin internal combustion engines when subjected to conditions of operation which comprises maintaining between bearing surfaces, oneof which is an alloy formed chiefly of a metal selected from the class consisting of cadmium and copper, a fllin of lubricating oil which initially produces an effective .lubricating action but which would normally tend to corrode the aforesaid alloy,

and maintaining the effectiveness of the lubricating oil by incorporating therein tributyl phosphite in a small but suiillcient proportion substantially to retard the corrosion. a

2. A method of lubricating bearingsurfaces in internal combustion engines when subjected to conditions of operation, which comprises maintaining between bearing surfaces, one of which is an alloy formed chiefly of a metal selected from the class consisting of cadmium and copper, a fllm of lubricating oil which initially produces an' eflective lubricating action but which would normally tend to corrode the aforesaid alloy, and maintaining the effectiveness of the lubricating oil by incorporating therein up to 1.0 per cent of tributyl phosphite sufllcient substantially to retard the corrosion.

3. A method of lubricating bearing surfaces which comprises maintaining between bearing surfaces, one of which is an alloy selected from the class consisting of cadmium-silver, cadmium-nickel, and copper-lead alloys, a film of lubricating oil which initially produces an eflective lubricating action but which would normally tend to corrode the aforesaid alloy and maintain- "ing the'efiectiveness of the lubricating oil by incorporating therein tributyl phosphite in a small but suillcient proportion substantially to retard the corrosion.

4. A method of lubricating bearing surfaces which comprises maintaining between the bearing surfaces, one of which contains a characterizing proportion of cadmium, silver, nickel, copper or lead, a film of lubricating oil which initially produces an effective lubricating action but which would normally tend to corrode the aforesaid surface and maintaining the effectiveness of the lubricating oil by incorporating therein tributyl phosphite in a, small but sufllcient proportion to substantially retard the corrosion.

WILLIAM WHITNEY WEINRICHQ 

